1. Field of the Invention
The present invention relates to compounds which are effective as catalysts for dismutating superoxide and, more particularly, the manganese or iron complexes of substituted, unsaturated heterocyclic pentaazacyclopentadecane ligands which catalytically dismutate superoxide.
2. Related Art
The enzyme superoxide dismutase catalyzes the conversion of superoxide into oxygen and hydrogen peroxide according to equation (1) (hereinafter referred to as dismutation). EQU 2O.sub.2.sup.- +2H.sup.+.fwdarw.O.sub.2 +H.sub.2 O.sub.2 (1)
Reactive oxygen metabolites derived from superoxide have been demonstrated to contribute to the tissue pathology in a number of inflammatory diseases and disorders, such as reperfusion injury to the ischemic myocardium, inflammatory bowel disease, rheumatoid arthritis, osteoarthritis, atherosclerosis, hypertension, metastasis, psoriasis, organ transplant rejections, radiation-induced injury, asthma, influenza, stroke, burns and trauma. See, for example, Simic, M. G., et al, Oxygen Radicals in Biology and Medicine, Basic Life Sciences, Vol. 49, Plenum Press, New York and London, 1988; Weiss, J. Cell. Biochem., 1991 Suppl. 15C, 216 Abstract C110 (1991); Petkau, A., Cancer Treat. Rev. 13, 17 (1986); McCord, J. Free Radicals Biol. Med., 2, 307 (1986); and Bannister, J. V. et al, Crit. Rev. Biochem., 22, 111 (1987).
It is also known that superoxide is involved in the breakdown of endothelium-derived vascular relaxing factor (EDRF), which has been identified as nitric oxide (NO), and that EDRF is protected from breakdown by superoxide dismutase. This suggests a central role for activated oxygen species derived from superoxide in the pathogenesis of hypertension, vasospasm, thrombosis and atherosclerosis. See, for example, Gryglewski, R. J. et al., "Superoxide Anion is Involved in the Breakdown of Endothelium-derived Vascular Relaxing Factor", Nature, Vol. 320, pp. 454-56 (1986) and Palmer, R. M. J. et al., "Nitric Oxide Release Accounts for the Biological Activity of Endothelium Derived Relaxing Factor", Nature, Vol. 327, pp. 523-26 (1987).
Clinical trials and animal studies with natural, recombinant and modified superoxide dismutase enzymes have been completed or are ongoing to demonstrate the therapeutic efficacy of reducing superoxide levels in the disease states noted above. However, numerous problems have arisen with the use of the enzymes as potential therapeutic agents, including lack of oral activity, short half-lives in vivo, immunogenicity of nonhuman derived enzymes, and poor tissue distribution.
In an effort to overcome the problems associated with superoxide dismutase enzymes, several investigations have been made into the design of non-proteinaceous catalysts for the dismutation of superoxide, and their use in various superoxide-related ailments. One group of catalysts which has been shown to be nearly as effective catalysts as the native superoxide dismutase enzymes are the manganese and iron complexes of pentaazacyclopentadecane ligands, described in U.S. Pat. Nos. 5,610,293, 5,637,578, and 5,874,421. These ligands are described as a pentaazacyclopentadecane macrocycle with various substituents on the carbons of the macrocycle, or with cyclic or heterocyclic structures attached to the carbons of the macrocycle. These compounds have been shown to possess catalytic superoxide dismutating activity as well as anti-inflammatory activity and to prevent oxidative damage. In addition, these compounds have been shown to possess analgesic activity in the rat-paw carrageenan hyperalgesia model, U.S. application Ser. No. 09/057,831. Two such described analgesic SOD mimic compounds are Compound A and Compound B: ##STR1##